It is known in the art to retain the piston or body of an engine valve train lash adjuster by means of a C-clip positioned in a groove of the piston and engaging an abutment in the periphery of the cylinder in which the lash adjuster is installed. For example, a hydraulic element assembly or lash adjuster may be retained in a cylinder baffle of a direct acting cam follower; or a hydraulic lash adjuster by having a swivel foot for engaging a valve or other component may be retained in a cylinder recess of an associated rocker arm.
Typically in such arrangements, the C-clip is formed of resilient spring wire biased to spring outward against a bore or abutment in which the piston is reciprocably retained. The C-clip is retained in a groove on the exterior of the piston The groove has a depth such that, when added to the diametral clearance be een the piston and cylinder, the total exceeds the diameter of the spring wire of the C-clip. This is necessary to allow installation of the piston into a closed end cylinder without scratching or otherwise damaging the associated cylinder wall. The retaining groove typically has a cylindrical er surface and opposed upper and lower end surfaces, which are generally radial but may be sloped slightly outward for tool clearance.
To allow installation of the piston or body in a cylinder, the entry opening of the cylind r is generally angled to provide a lead-in cone angle. The cone angle com resses the C-clip into the piston groove and allows the piston with clip installed to be slid into the closed end cylinder and past a retaining abutment into operating position. The retaining abutment may be, for example, the upper edge of a baffle tube of a direct acting cam follower and its configuration is important in determining the ability of the C-clip to retain the hydraulic element assembly (HEA) in the cam follower cylinder.
For example, if the upper edge of the baffle tube is formed with a surface normal to the axis of the cylinder, that is horizontal when the cylinder axis is vertical, the retention of the piston in the cylinder by the expanded C-clip will be at a maximum since the horizontal or normal surface will not provide a substantial radial force for compressing the C-clip into the groove. Thus, if removal of the HEA is desired, it may be necessary to shear off the retaining parts of the C-clip in order to disassemble the assembly.
Since disassembly is sometimes required for inspection or replacement, the inner edge or abutment of the cylinder or baffle tube is generally sloped or angled downward and inward to provide a conical surface that engages the C-clip when retention or removal is desired. This angle may be varied as desired in order to maintain a sufficient force to retain the piston in place under anticipated operating conditions, while having a sufficient slope to allow removal of the lash adjuster or HEA from the cylinder when desired, without damaging the cylinder or HEA surface. The selection of the installation and retention angles on the cylinder edges is determined in part by the actual configuration of the C-clip and the diameter of wire from which it is made, as well as the depth of the retaining groove in which it is installed. These factors then, as well as the resilient force applied in expansion of the C-clip, all have a bearing on the selection of angles for accomplishing the various desired purposes of retention and ability to remove the HEA or lash adjuster when desired.